Stabilization in the braid groups I: MTWS

Choose any oriented link type X and closed braid representatives X[+], X[-] of X, where X[-] has minimal braid index among all closed braid representatives of X. The main result of this paper is a `Markov theorem without stabilization'. It asserts that there is a complexity function and a finite set of `templates' such that (possibly after initial complexity-reducing modifications in the choice of X[+] and X[-]which replace them with closed braids X[+]', X[-]') there is a sequence of closed braid representatives X[+]' = X^1->X^2->...->X^r = X[-]' such that each passage X^i->X^i+1 is strictly complexity reducing and non-increasing on braid index. The templates which define the passages X^i->X^i+1 include 3 familiar ones, the destabilization, exchange move and flype templates, and in addition, for each braid index m>= 4 a finite set T(m) of new ones. The number of templates in T(m) is a non-decreasing function of m. We give examples of members of T(m), m>= 4, but not a complete listing. There are applications to contact geometry, which will be given in a separate paper.